This application is the National Phase Filing of PCT International Application No. PCT/TR98/00008, filed May 26, 1997, published Dec. 3, 1998, as Publication No. WO 98/54108, the full disclosures of which are incorporated by reference herein.
1. Field of the Invention
The present invention relates to admixtures production and to method of the admixtures application in cement and concrete technology. The method allows to produce high-strength and high durable cement based systems, as well as cement systems with specially designed properties or cheap high-volume mineral admixture cements.
2. Description of the Prior Art
The admixtures for cement systems, especially high range water reducers or superplasticizers, have significant influence on strength and durability of concrete due to ability to reduce water demand and provide low porosity and permeability. The usage of such admixtures allows to produce concrete with high level of properties. The application of new high range water reducing agents for production of ultra high-strength concrete is explained in some U.S. patents (U.S. Pat. No. 5,466,289). Advantages of the high strength and high durable concrete have provided their large-scale applications in construction projects such as high-rise buildings, bridges, marine and offshore structures, tunnels, parking desks, repairing of structures, etc.
There are many products marketed as high range water reducers for concrete. The original composition of high range water reducers is protected by numbers of International patents (for instance, in U.S. Pat. No. 5,584,920; 5,494,516; 4,704,415; 4,460,720 and 4,441,929) and it is well-known that essentially they are lignosulphonates-, melamine-, naphthalene- and polyacrylate-based compounds. The process of water reduces production is realised in aqueous solution and the final product contains 55-75% of water. Application of water reducers in aqueous solution is impossible for some dry production process, such as cement and dry mortar. Usage of dry or semi-dry water reducers is more attractive for ready mix and precast concrete plant or construction site due to the reason of easy transportation and storage. For such projects dry powder water reducers are available. Production cost of the powder admixtures rises up to two times because drying process in special apparatus is used to remove water. Development of the cheapest process for the dry- or semi-dry water reducing admixtures would be useful to extend the frames of their application.
Process explained in U.S. Pat. No. 4,297,309 (except final procedure of firing) that allow to produce articles with different shape based on fine silica particles and water is very close to present invention. Application of active calcium reactive sorbents for combining of some gas and liquid chemicals, especially for sulfur dioxide and metals, is also described in some U.S. patents (U.S. Pat. No. 5,405,535; 5,227,351). Usage of invented complex admixture in cement and concrete technology is similar to existing mode for mineral admixtures such as fly ash (U.S. Pat. No. 5,601,643) application.
The main difference of the present invention is ability to create economical combinations in sorbentxe2x80x94water reducer system that can be used as universal and super effective modifiers for cement systems. The available test results confirm that synergetic effect of sorbentxe2x80x94water reducer is multiplied in case of increasing of preliminary treatment of cementxe2x80x94invented modifier compositions in dry or liquid state. This advantages allow to achieve new level of properties or provide production of wide range of new and more economic cement based materials with conventional properties.
The present invention is directed to development of the dry and semi-dry admixtures composition and production process. The usage of active silicon dioxide based sorbents allows to combine water containing in water reducers and to produce new complex admixture for modifying of cement system. The main criterion of sorbents selection is compatibility with cement system, especially for long-term action. The correct combinations in sorbentxe2x80x94water reducer system allows to create wide range of universal and super effective modifiers for cement systems.
The method of the complex admixture application in cement and concrete technology allows to produce the high-strength and high durable cement based systems, as well as the cement systems with specially designed properties or cheap high-volume mineral admixtures cements. The method is based on modification of cement or dry mix in production process by invented complex admixtures. This allows to increase the compressive strength of cement based materials up to 145-180 MPa and/or to introduce a large quantity of mineral indigenous admixtures up to 70% in the cement composition.
The dry or semi-dry complex admixtures production process includes mixing of water reducer solution with powder components of active sorbents.
The most important component of the sorbent is presented by fine alkali reactive silicon dioxide based materials. Virtually any composition that includes fine or superfine non-crystalline silicon dioxide may be applied in the practice. Such compositions include, but are not limited by fly ash, rice husk ash, zeolite, silica fume, bentonite, activated kaolin, montmorillonite, diatomaceous earth, etc. The mass ratios of reactive silicon dioxide component to water reducer ranging from about 5:1 to about 100:1 are preferred.
Available high range water reducers, as well as their mix (including other admixtures) can be used. The best results are achieved in case of sulphonated melamine (SMF) or naphthalene (SNF) formaldehyde, as well as polyacrylate (PA) based high range water reducer application. The water content of high range water reducer component can be varied from about 25 to about 85%.
The high porous lightweight sand (with particles size less than 5 mm) can be used as water accumulating component of active sorbent. The wide range of natural and artificial lightweight materials, as volcanic pumice, tuff, expanded clay, expanded perlite, expanded slag, expanded glass, etc can be used. The mass ratios of reactive silica to accumulating porous component can be varied from about 10:1 to about 1:1.
The non-organic or organic salts or hydroxides of metals can be used as electrolytic agent, which provide better distribution and dissolving of the complex admixture particles in aqueous media. Such compositions include, but are not limited by metal (especially, alkali and alkali earth) aluminates, hydroxides and carbonates: sodium nitrite, sulphate Al, Na, K, Ca, calcium chloride, calcium formate, etc. The introduction of the electrolytic agent into process can be made before or together with reactive silica component mixing in order to provide better homogenisation of system. The mass ratios of reactive silica component to electrolytic agent can be varied from about 10:1 to about 1000:1. Accelerating effect on cement hardening process can be achieved in case of the composition application.
The hydrated, partially hydrated and dehydrated salts or combinations that are able to combine with water can be used to bond free water in the system. The water-combining component can be applied before, during or after mixing of the main composition. The last case provides the formation of the granules covered by dense protective layer. This solution may be very useful if total amount of water is high and due to some reasons reactive silica content can not be increased. The one or more types of calcium sulfate, high alumina cement or sulphate Na can be used as water combining component. The mass ratios of reactive silica to water combining component can be adjusted from about 1:1 to about 100:1. The effect of regulation of cement setting time, as well as accelerating of hardening process can be achieved for such composition.
The complex admixture can contain water-soluble polymer, which can be applied at any time during the main composition mixing. The usage of dry or aqueous dispersion of polymer, as well as combination of several polymers is possible. The introduction of the water-soluble polymer after mixing of the main composition provides the formation of the stronger granules. Acrylic acid or acrylic acid copolymers, polyvinyl alcohol, polyvinyl acetate, poly acryl amide, polyethylene oxide, cellulose ethers, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose can be applied in this composition. The mass ratio of reactive silica to water soluble polymer can be varied from about 3:1 to about 100:1. The usage of the complex admixtures containing water soluble polymer for cement modification allows to produce the systems with desired rheological behaviour, for instance, reduce the cement paste viscosity at the certain time, increase pumping of fresh mortar and concrete, as well as to improve some strength characteristics, as tensile, flexural, impact and bond strength, modulus of elasticity, etc.
The composition can contain any retarders of hydration, setting, and hardening of cement system. The retarders include, but are not limited by lignosulphonates, sugars, hydroxycarbonic acids and their salts, carboxylates, phosphonic or phosphoric acids, as well as their ethers and salts. The mass ratio of reactive silica to retarder can be chosen from about 50:1 to about 1000:1. The retarder application is more suitable for delaying of cement setting time, as well as for significant reduction of heat development.
The available air detraining, hydrophobic, air entraining, foaming and/or gas creating admixtures can be applied as component of the main composition. Three-butyl phosphate can be used as air detraining component. Silicon based compounds containing silicones, silanes, silanols or siloxanes groups such as alkyl alkoxy silanes can be used as hydrophobic components. Air entraining and foaming agents can be neutralised hydroaromatic and fatty carboxylic acid, tall oil, vinsol resin and protein-based admixtures. The powder of some metals (for example, aluminium), as well as hydrogen peroxide can be applied as gas creating admixture. The film and structure creating actions, as well as self-dissolving effects of these admixtures are used for production of well-performed complex products. The mass ratio of reactive silica to structure formation components can be varied from about 10:1 to about 10000:1. The usage of this kind of structure formation components provides necessary porous system of cement paste from dense non-porous to cellular lightweight structure. The hydrophobic components provide creation of super thin hydrophobic layer on porous area surface. The gas creating agents can be used also for elimination of shrinkage, production of expanding cements or accelerating of hardening and heat development for production self-curing systems.
Grinding aids can be submitted as component of the main composition. The triethanol amine, amine acetate salts, EDTA, acetic acid, hydrocarbons, silanes, methyl chlorine or fluorine silanes, etc can be used as grinding aid components. The effect of grinding acceleration is achieved due to reducing of agglomeration and surface tension. The mass ratio of reactive silica to grinding aid components can be varied from about 10:1 to about 10000:1.
The main idea of the mix proportioning is to create workable, dry or semi-dry complex admixture that meets the cost/benefit requirements and has significant improving influence on cement system properties. The presented mix design also provides protection against undesirable reaction between the complex admixture components, mainly, due to high content of water reducer and small amount of water available for such reaction.
Any mixing process can be applied in the practice to meet the main requirement of composition homogenising. The promising results are demonstrated by the high speed mixers (spindle or planetary type), vibrating mixers or mills, as well as the air jet mixers or mills. In case, if necessary, any types of the granulating equipment can be used for finishing of the complex admixture. The product as per the invention might be presented by wide range of coarse and fine granules. The quality the complex admixture can be improved by drying, pressing, extrusion, crushing, calendering, etc. The required physical characteristics, as well as better homogenising of composition, necessary fineness and shape are achieved by means of such treatment.
The introduction of the complex admixture into cement or dry mix production process allows to increase the compressive strength of these materials up to 145-180 MPa. The cement composition can contain portland cement clinker including one or more combination of calcium silicates and/or calcium aluminates and one or more types of calcium sulfate, or portland cement with Blaine specific surface area less than 400 m/kg and the complex admixture. The mass ratio of portland cement to complex admixture can be varied from about 100:1 to about 2:1. The chemical composition of clinker and cement can vary in the limits of existing standards or special clinker and cement can be used. Generally, any kind of existing cements can be applied in this composition. (for example, in accordance with ASTM C150, C595, C845, C91 or prEN197-1) This cements include, but are not limited by general use cements, moderate heat of hardening cements, high early strength cements, low heat cements, sulfate resisting cements, white portland cements, blended hydraulic cements, portland blast furnace slag cements, portland-pozzolan cements, special cements, expanding cements, high alumina cements, oil-well cements, etc, as well as any combination and mix of this cements.
The large quantity up to 70% of mineral indigenous admixtures can be introduced in the cement composition. The natural materials as pozzolans, volcanic glasses, diatomaceous earth, perlite, tuff volcanic pumice, natural sand, quarts, marble, limestone, burnt gaize, burnt clay, burnt shale, rice husk ash, bentonite, activated kaolin, etc and industrial by-products or wastes as granulated blast furnace slag, fly ash, silica fume, catalytic and alum wastes, broken glass and ceramic, calcium sulfate, etc can be used as mineral admixtures. Selection of special mineral admixtures, for instance with high density, chemical, thermal or abrasion resistance, thermal expansion, electric conductivity etc allow to produce cement systems with specially designing and unique properties. The mass ratio of mineral indigenous admixtures to complex admixture can be varied from about 100:1 to about 1:1. Maximum quantity of mineral admixtures in the cement composition depends on type of mineral admixtures, as well as strength and durability level required.
The dry mix can contain specially selected dry aggregates (for example, in accordance with ASTM C387 or C33). The mass ratio of aggregates to total cementing material (cement, mineral admixtures and complex admixture) can be varied from about 10:1 to about 1:2.
The existing apparatus and technologies can be used for cement or dry mix production process. Satisfactory results were achieved by the application of high speed mixers (for dry mix or blended cement production), vibrating mixers or mills, air jet mixers or mills, ball mills, tube ball mills (for cement production). The mode of complex admixture introduction into portland cementxe2x80x94mineral admixturesxe2x80x94aggregates systems covers all possible combinations. Adequately formula was concluded in case if portland cement clinker and calcium sulfate (or portland cement as component) and the complex admixture was interground in mill (preferable, open cycle ball mill). The product in accordance with the formula is presented by modified super high strength cement, which can be used as final product or for consequent production of the blended cements (by inter grinding or mixing with mineral admixtures) and dry mix (by mixing with aggregates). Joint interground clinker (or portland cement)xe2x80x94mineral admixturexe2x80x94complex admixture system also possessed high level of properties. Separate grinding of clinker and mineral admixture components and consequent intergrinding or mixing with complex admixture allows to design systems with very small water demand due to optimal and dense particles packing.
The concrete and mortars based on modified cements posses high strength and high durability, as well as excellent workability and pumping. The wide range of aggregates and fibrous materials (as polypropylene, nylon, glass) can be used for concrete and mortars production. Introduction of the complex admixture as component of concrete mix is also possible, and for this case usage of pre-mixer is recommended. Good mixing effect is achieved if complex admixture, water and part of cement were pre-mixed in colloid mixer. Selection of special fillers and/or aggregates for concrete, for instance with high density, chemical, thermal or abrasion resistance, thermal expansion, electric conductivity etc allow to design the wide range of concrete with special and unique properties.
The complex admixture modified cement paste, mortar or concrete based materials can be used after any kind of consequent treatment in fresh or hardening state. These treatment processes include, but are not limited by vibrating, pressing, extrusion, calendering, drying, heat or autoclave treatment, etc. The required properties of products can be achieved by means of such treatment.
The invention can be described by the following examples which can explain the advantages of complex admixture application in cement and concrete technology and demonstrate the opportunity of production of the cement based systems with unique properties. The examples are not intended to limit the scope of the invention. In what follows, xe2x80x9c%xe2x80x9d will mean xe2x80x9cweight %xe2x80x9d, xe2x80x9cratioxe2x80x9d will mean xe2x80x9cweight ratioxe2x80x9d and xe2x80x9cpartsxe2x80x9d will mean xe2x80x9cweight partsxe2x80x9d.